Thanks for all the info on this thread - was surprised how straightforward it was to replace the IWEs on my truck (were still original, at 178000 miles).

It's been cold (averaging -5 degrees F over the past few months) so I was being lazy and was waiting for a warmer day

The IWE on my passenger side had me stumped since it held vacuum, yet still caused the halfshaft to turn when I spun the tire with vacuum applied. Turned out the IWE had fallen apart. I wonder if that was related to work that the dealer had done on that hub recently - to me it seemed that the shaft end nut was on a bit loose when I removed it.

I didn't want to jump on and start a new thread for a topic that has been addressed so thoroughly, but I am still having trouble trying to get my 4WD working. I have been through every IWE thread on multiple forums and am still having some trouble. Hope some of you who have been through this could help.

I have replaced both IWE's, the Vacuum Solenoid, and the Vacuum Reservior. I have been through all the vacuum lines and checked all the fuses and relays in the systems.

When the engine is running and the front is in the air, both tires spin free of the half shafts as they should. When I pull the vacuum line off the IWE's, the four wheel drive works as it should.

I figured the new solenoid must be bad, but when I jumpered 12V to the solenoid, and I can hear it opening and closing like it should.

What is confusing me is when I check voltage at the plug to the Vacuum Solenoid, I get 12V with the switch in both 2WD and 4WD. As I understand it, I should get a zero voltage reading in one of those settings (sorry, I don't remember which setting closes the groud path, but one setting should be open and one should be closed.)

Where does the signal to the solenoid come from? As I mentioned, the T case is engaging, and the driverline is doing what it should, but I can't seem to kill vacuum to the system? I'm running out of things to check...

Hey all, I have a 2008 F150 STX 4x4 and tonight all of the sudden while driving when I engaged 4WD High I got a grinding noise on the drivers side front. I turned off 4WD and it went away. I tried it again and it came back. I am not sure if 4WD stayed engaged as I didn't want to cause any damage to the system so I turned it off right away. As soon as I had a chance I pulled over and put it in neutral and engaged 4WD Low. That seemed to be fine, the system had a small whine which I think might be normal. Do you think this is something to with the vacuum or a bearing or something? Should I post a new thread? Thanks for all the great help on here.

Like William, I have an identical problem but more to it. And since this seems like the part of the forum to address it, here it goes. I have a 2003 F250 5.4 4WD with a 4" Icon lift.

A couple of months ago it started out with a high rotational squeak sound coming from the front driver's side. Tried stomping on the brakes to see if it went away >> it didn't. It eventually went away on its own.

Once the snow arrived I noticed a grinding "feel" in the front end when I put it in 4WD High. Tried switching to 4WD Low, fwd/reverse, etc to no avail. Depending on the snow conditions, I tried to keep it out of 4WD as much as I could until I could have it looked at.

Today, the high pitched squeal came back AND it was snowing. The squeal went away when I put it in 4WD, but I got the grinding. I took it out of 4WD, but then got the squeal again. For better or worse, now I know the 2 items are connected.

On top of all that, I took a look at the front differential/axle and notice a hose off. I'm assuming this is a vacuum hose since it's only approx 2' long, attached to the frame. It's cracked on the end so I need to replace. I'm pretty sure it's a vacuum hose that's supposed to have a plug in the end, but it doesn't.

I've been thru the thread, all 22 pages of them, and I have a burning question. If the half shafts turn when the 4WD is engaged, but the wheels don't move, what is the problem? Is it in the IWE (what does that mean?) vacuum system or in the hub?

We put the 4 corners up today, and ran the truck with no wheels on the ground. With the 2WD engaged, the front wheels can be turned over with or without the engine running. When either the 4WH of 4WL are engaged, the same is true, and the the wheels can turned in reverse while the half-shafts are turning forward. We're still recovering from PAX and REX here in MD, so we have to clear snow from the place to do these checks and work.

Any ideas are greatly appreciated. I am just baffled...

Last edited by ironbandit; 02-18-2014 at 06:59 PM.
Reason: didn't see 7 pages of posts...

I found my 4WD not working on an icy hill this weekend. The dash light worked and and the transfer case was able to shift into low range, so that seemed good as well. I disconnected the output vacuum line from the solenoid and found that it still pulled vacuum no matter the position of the 4WD switch. Must be frozen open. My truck is an 08 KR so it does have the porch buillt over the solenoid. Anyway, I capped off the line and the hubs engaged. I'll just leave them engaged until its warn enough outside for me to not mind working out there.

One other note. While fumbling with the output line to disconnect it, it broke very easily in my hands so it looks like a vacuum line reroute is in order as well.

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